N-oxides of heterocyclic esters, amides, thioesters, and ketones

ABSTRACT

This invention relates to neurotrophic low molecular weight, small molecule N-oxides of heterocyclic esters amides, thioesters, and ketones having an affinity for FKBP-type immunophilins, and their use as inhibitors of the enzyme activity associated with immunophilin proteins, particularly peptidyl-prolyl isomerase, or rotamase, enzyme activity.

This application is a continuation of Ser. No. 09/556,482, Aug. 21,2000, U.S. Pat. No. 6,251,895 which is a continuation of Ser. No.09/112,319 Jul. 9, 1998 U.S. Pat. No. 6,054,452 which is a continuationof Ser. No. 08/807,406, Feb. 28, 1997, U.S. Pat. No. 5,846,979.

BACKGROUND OF THE INVENTION

1. Field of Invention

This invention relates to neurotrophic low molecular weight, smallmolecule N-oxides of heterocyclic esters having an affinity forFKBP-type immunophilins, and their use as inhibitors of the enzymeactivity associated with immunophilin proteins, particularlypeptidyl-prolyl isomerase, or rotamase, enzyme activity.

2. Description of Related Art

The term immunophilin refers to a number of proteins that serve asreceptors for the principal immunosuppressant drugs, cyclosporin A (CsA)FK506 and rapamycin. Known classes or immunophilins are cyclophilins andFK506 binding proteins, or FKBPs. Cyclosporin A binds to cyclophilin Awhile FK506 and rapamycin bind to FKBP12. These immunophilin-drugcomplexes interface with various intracellular signal transductionsystems, especially the immune and nervous systems.

Immunophilins are known to have peptidyl-prolyl isomerase (PPIase) , orrotamase, enzyme activity. It has been determined that rotamase enzymeactivity plays a role in the catalyzation of the interconversion of thecis and trans isomers of peptide and protein substrates for theimmunophilin proteins.

Immunophilins were originally discovered and studied in the immunetissue. It was initially postulated by those skilled in the art thatinhibition of the immunophilins' rotamase activity leads to inhibitionof T-cell proliferation, thereby causing the immunosuppressive activityexhibited by the immunosuppressant drugs, such as cyclosporin A, FK506and rapamycin. Further study has shown that the inhibition of rotamaseactivity, in and of itself, does not result in immunosuppressiveactivity. Schreiber et al., Science, 1990, vol. 250, pp. 556-559.Instead, immunosuppression appears to stem from the formulation of acomplex of immunosuppressant drugs and immunophilins. It has been shownthat the immunophilin-drug complexes interact with ternary proteintargets as their mode of action. Schreiber et al., Cell, 1991, vol. 66,pp. 807-815. In the case of FKBP-FK506 and cyclophilin-CsA, theimmunophilin-drug complexes bind to the enzyme calcineurin and inhibitthe T-cell receptor signalling which leads to T-cell proliferation.Similarly, the immunophilin-drug complex of FKBP-rapamycin interactswith the RAFT1/FRAP protein and inhibits the IL-2 receptor signalling.

Immunophilins have been found to be present at high concentrations inthe central nervous system. Immunophilins are enriched 10-50 times morein the central nervous system than in the immune system. Within neuraltissues, immunophilins appear to influence nitric oxide synthesis,neurotransmitter release and neuronal process extension.

It has been found that picomolar concentrations of an immunosuppressantsuch as FK506 and rapamycin stimulate neurite outgrowth in PC12 cellsand sensory neurons, namely dorsal root ganglion cells (DRGs) Lyons etal., Proc. of Natl. Acad. Sci., 1994, vol. 91, pp. 3191-3195. In wholeanimal experiments, FK506 has been shown to stimulate nerve regenerationfollowing facial nerve injury.

Surprisingly, it has been found that certain compounds with a highaffinity for FKBPs are potent rotamase inhibitors and exhibit excellentneurotrophic effects. Furthermore, these rotamase inhibitors are devoidof immunosuppressive activity. These findings suggest the use ofrotamase inhibitors in treating various peripheral neuropathies andenhancing neuronal regrowth in the central nervous system (CNS). Studieshave demonstrated that neurodegenerative disorders such as Alzheimer'sdisease, Parkinson's disease, and amyotrophic lateral sclerosis (ALS)may occur due to the loss, or decreased availability, of a neurotrophicsubstance specific for a particular population of neurons affected inthe disorder.

Several neurotrophic factors affecting specific neuronal populations inthe central nervous system have been identified. For example, it hasbeen hypothesized that Alzheimer's disease results from a decrease orloss of nerve growth factor (NGF). It has thus been proposed to treatSenile Dementia Alzheimer's Type (SDAT) patients with exogenous nervegrowth factor or other neurotrophic proteins, such as brain derivedgrowth factor, glial derived growth factor, ciliary neurotrophic factorand neurotropin-3, to increase the survival of degenerating neuronalpopulations.

Clinical application of these proteins in various neurological diseasestates is hampered by difficulties in the delivery and bioavailabilityof large proteins to nervous system targets. By contrast,immunosuppressant drugs with neurotrophic activity are relatively smalland display excellent bioavailability and specificity. However, whenadministered chronically, immunosuppressant drugs exhibit a number ofpotentially serious side effects including nephrotoxicity, such asimpairment of glomerular filtration and irreversible interstitialfibrosis (Kopp et al., J. Am. Soc. Nephrol., 1991, 1:162); neurologicaldeficits, such as involuntary tremors, or non-specific cerebral angina,such as non-localized headaches (De Groen et al., N. Engl. J. Med.,1987, 317:861); and vascular hypertension with complications resultingtherefrom (Kahan, et al., N. Engl. J. Med., 1989, 321:1725)

In order to prevent the side effects associated with use of theimmunosuppressant compounds, the present invention providesnon-immunosuppressive compounds containing small molecule FKBP rotamaseinhibitors for enhancing neurite outgrowth, and promoting neuronalgrowth and regeneration in various neuropathological situations whereneuronal repair can be facilitated, including: peripheral nerve damagecaused by physical injury or disease state such as diabetes; physicaldamage to the central nervous system (spinal cord and brain); braindamage associated with stroke; and neurological disorders relating toneurodegeneration, such as Parkinson's disease, SDAT (Alzheimer'sdisease), and amyotrophic lateral sclerosis.

SUMMARY OF THE INVENTION

The present invention relates to neurotrophic low molecular weight,small molecule compounds having an affinity for FKBP-type immunophilins.Once bound to these proteins, the neurotrophic compounds are potentinhibitors of the enzyme activity associated with immunophilin proteins,particularly peptidyl-prolyl isomerase, or rotamase, enzyme activity. Akey feature of the compounds of the present invention is that they donot exert any significant immunosuppressive activity in addition totheir neurotrophic activity. Another significant feature is the noveladdition of the oxidation of specific amine groups to the correspondingN-oxide to provide an unexpected increase in bioavailability and potencyas compared to compounds lacking the N-oxide group.

Specifically, the present invention relates to a compound of formula I:

or a pharmaceutically acceptable salt thereof, wherein:

A and B are taken together, with the nitrogen and carbon atoms to whichthey are respectively attached, to form a 5-7 membered saturated orunsaturated heterocyclic ring containing any combination of CH₂, O, S,SO, SO₂, NH or NR₁ in any chemically stable oxidation state;

W is O, S, CH₂, or H₂;

R is a C₁-C₆ straight or branched chain alkyl or alkenyl groupoptionally substituted with C₃-C₉ cycloalkyl, C₃ or C₅ cycloalkyl, C₅-C₇cycloalkenyl, or Ar₁, where said alkyl, alkenyl, cycloalkyl, orcycloalkenyl groups may be optionally substituted with C₁-C₄ alkyl,C₁-C₄ alkenyl, or hydroxy, and where Ar₁ is selected from the groupconsisting of 1-napthyl, 2-napthyl, 1-indolyl, 2-indolyl, 2-furyl,3-furyl, 2-thienyl, 3-thienyl, 2-pyridyl, 3-pyridyl, 4-pyridyl, orphenyl, having one to three substituents which are independentlyselected from the group consisting of hyrogen, halo, hydroxyl, nitro,trifluoromethyl, C₁-C₅ straight or branched alkyl or alkenyl, C₁-C₄alkenyloxy, phenoxy, benzyloxy, and amino;

X is O, NH, NR₁, S, CH, CR₁, or C(R₁)₂;

Y is a direct bond, or a C1-C₆ straight or branched chain alkyl oralkenyl which is optionally substituted in one or more positions withC₁-C₆ straight or branched chain alkyl or alkenyl, or C₃-C₈ cycloalkyl,or C₅-C₇ cycloalkenyl, or hydroxyl, or carbonyl oxygen, or with Ar,where said alkyl, alkenyl, cycloalkyl, cycloalkenyl, or Ar group isoptionally substituted with C₁-C₄ alkyl, C₁-C₄ alkenyl, or hydroxy, orcarbonyl oxygen, or wherein any of the carbon atoms or said alkyl,alkenyl, cycloalkyl, cycloalkenyl, or Ar group is optionally replacedwith O, NH, NR₂, S, SO, or SO₂, where R₂ is selected from the groupconsisting of hydrogen, (C₃-C₄)-straight or branched chain alkyl,(C₃-C₄) -straight or branched chain alkenyl or alkynyl, and (C₁-C₄)bridging alkyl wherein a bridge is formed between the nitrogen and acarbon atom of said alkyl or alkenyl chain containing said heteroatom toform a ring, wherein said ring is optionally fused to an Ar group; and

Z is an aromatic or tertiary alkyl amine oxidized to a correspondingN-oxide, wherein the aromatic amine is Ar oxidized to a correspondingN-oxide where Ar is a mono-, bi- or tricyclic, carbo- or heterocyclicring, wherein the ring is either unsubstituted or substituted in one tothree position(s) with halo, hydroxyl, nitro, trifluoromethyl, C₁-C₅straight or branched chain alkyl or alkenyl, C₁-C₄ alkoxy, C₁-C₄alkenyloxy, phenoxy, benzyloxy, amino, or a combination thereof; whereinthe individual ring sizes are 5-6 members; wherein the heterocyclic ringcontains 1-6 heteroatom(s) selected from the group consisting of O, N,S, and a combination thereof wherein at least one of the heteroatoms isN, and wherein the alkyl amine is oxidized to a corresponding N-oxidewhere alkyl is a C₁-C₆ straight or branched chain alkyl or alkenyl whichis optionally substituted in one or more positions with C₁-C₆ straightor branched chain alkyl or alkenyl, or C₃-C₈ cycloalkyl, or C₅-C₇cycloalkenyl, or hydroxyl, or carbonyl oxygen, or with Ar, where saidalkyl, alkenyl, cycloalkyl, cycloalkenyl, or Ar group is optionallysubstituted with C₁-C₄ alkyl, C₁-C₄ alkenyl, or hydroxy, or carbonyloxygen, or wherein any of the carbon atoms of said alkyl, alkenyl,cycloalkyl, cycloalkenyl, or Ar group is optionally replaced with O, NH,NR₁, S, SO, or SO₂; and,

R₁ is hydrogen, (C₁-C₄) -straight or branched chain alkyl, (C₃-C₄)-straight or branched chain, alkenyl or alkynyl, or R₁ is Y-Z, asdefined above.

Another preferred embodiment of this invention is a compound of formulaII:

or a pharmaceutically acceptable salt thereof, wherein:

E, F, G and H are independently CH₂, O, S, SO, SO₂, NH or NH₁;

W is C, S, CH₂, or H₂;

R is a C₁-C₆ straight or branched chain alkyl or alkenyl groupoptionally substituted with C₃-C₈ cycloalkyl, C₃ or C₅ cycloalkyl, C₅-C₇cycloalkenyl, or Ar₁, where said alkyl, alkenyl, cycloalkyl, orcycloalkenyl groups may be optionally substituted with C₁-C₄ alkyl,C₁-C₄ alkenyl, or hydroxy, and where Ar₁ is selected from the groupconsisting of 1-napthyl, 2-napthyl, 1-indolyl, 2-indolyl, 2-furyl,3-furyl, 2-thienyl, 3-thienyl, 2-pyridyl, 3-pyridyl, 4-pyridyl, orphenyl, having one to three substituents which are independentlyselected from one group consisting of hyrogen, halo, hydroxyl, nitro,trifluoromethyl, C₁-C₆ straight or branched alkyl or alkenyl, C₁-C₄alkenyloxy, phenoxy, benzyloxy, and amino;

X is O, NH, NR₁, S, CH, CR₁, or C(R₁)₂;

Y is a direct bond, or a C1-C₆ straight or branched chain alkyl oralkenyl which is optionally substituted in one or more positions withC₁-C₆ straight or branched chain alkyl or alkenyl, or C₁-C₈ cycloalkyl,or C₅-C₇ cycloalkenyl, or hydroxyl, or carbonyl oxygen, or with Ar,where said alkyl, alkenyl, cycloalkyl, cycloalkenyl, or Ar group isoptionally substituted with C₁-C₄ alkyl, C₁-C₄ alkenyl or hydroxy, orcarbonyl oxygen, or wherein any of the carbon atoms or said alkyl,alkenyl, cycloalkyl, cycloalkenyl, or Ar group is optionally replacedwith O, NH, NR₂, S, SO, or So₂, where R₂ is selected from branched chainalkyl, (C₃-C₄) -straight or branched chain alkenyl or alkynyl, and(C₁-C₄) bridging alkyl wherein a bridge is formed between the nitrogenand a carbon atom of said alkyl or alkenyl chain containing saidheteroatom to form a ring, wherein said ring is optionally fused to anAr group; and

Z is an aromatic or tertiary alkyl amine oxidized to a correspondingN-oxide, wherein the aromatic amine is Ar oxidized to a correspondingN-oxide where Ar is a mono-, bi- or tricyclic, carbo- or heterocyclicring, wherein the ring is either unsubstituted or substituted in one tothree position(s) with halo, hydroxyl, nitro, trifluoromethyl, C₁-C₅straight or branched chain alkyl or alkenyl, C₁-C₄ alkoxy, C₁-C₄alkenyloxy, phenoxy, benzyloxy, amino, or a combination thereof; whereinthe individual ring sizes are 5-6 members; wherein the heterocyclic ringcontains 1-5 heteroatom(s) selected from the group consisting of O, N,S, and a combination thereof wherein at least one of the heteroatoms isN, and wherein the alkyl amine is oxidized to a corresponding N-oxidewhere alkyl is a C₁-C₆ straight or branched chain alkyl or alkenyl whichis optionally substituted in one or more positions with C₁-C₆ straightor branched chain alkyl or alkenyl, or C₃-C₈ cycloalkyl, or C₅-C₇cycloalkenyl, or hydroxyl, or carbonyl oxygen, or with Ar, where saidalkyl, alkenyl, cycloalkyl, cycloalkenyl, or Ar group is optionallysubstituted with C₁-C₄ alkyl, C₁-C₄ alkenyl, or hydroxy, or carbonyloxygen, or wherein any of the carbon atoms of said alkyl, alkenyl,cycloalkyl, cycloalkenyl, or Ar group is optionally replaced with O, NH,NR₁, S, SO, or SO₂; and,

R₁ is hydrogen, (C₁-C₄) -straight or branched chain alkyl, (C₃-C₄)-straight or branched chain alkenyl or alkynyl, or R₁ is Y-Z, as definedabove.

Another preferred embodiment s a compound of formula III:

or a pharmaceutically acceptable salt thereof, wherein:

E, F, and G are independently CH₂, O, S, SO, SO₂, NH or NR₁;

W is O, S, CH₂, or H₂;

R is a C₁-C₆ straight or branched chain alkyl or alkenyl groupoptionally substituted with C₃-C₈ cycloalkyl, C₃ or C₅ cycloalkyl, C₅-C₇cycloalkenyl, or Ar₁, where said alkyl, alkenyl, cycloalkyl, orcycloalkenyl groups may be optionally substituted with C₁-C₄ alkyl,C₁-C₄ alkenyl, or hydroxy, and where Ar₁ is selected from the groupconsisting of 1-napthyl, 2-napthyl, 1-indolyl, 2-indolyl, 2-furyl,3-furyl, 2-thienyl, 3-thienyl, 2-pyridyl, 3-pyridyl, 4-pyridyl, orphenyl, having one to three substituents which are independentlyselected from the group consisting of hyrogen, halo, hydroxyl, nitro,trifluoromethyl, C₁-C₆ straight or branched alkyl or alkenyl, C₁-C₄alkenyloxy, phenoxy, benzyloxy, and amino;

X is O, NH, NR₁, S, CH, CR₁, or C(R₁)₂;

Y is a direct bond, or a C1-C₆ straight or branched chain alkyl oralkenyl which is optionally substituted in one or more positions withC₁-C₆ straight or branched chain alkyl or alkenyl, or C₁-C₃ cycloalkyl,or C₅-C₇ cycloalkenyl, or hydroxyl, or carbonyl oxygen, or with Ar,where said alkyl, alkenyl, cycloalkyl, cycloalkenyl, or Ar group isoptionally substituted with C₁C₄ alkyl, C₁-C₄ alkenyl, or hydroxy, orcarbonyl oxygen, or wherein any of the carbon atoms of said alkyl,alkenyl, cycloalkyl, cycloalkenyl, or Ar group is optionally replacedwith O, NH, NR₂, S, SO, or SO₂, where R₂ is selected from the groupconsisting of hydrogen, (C₁-C₄) -straight or branched chain alkyl,(C₁-C₄) -straight or branched chain alkenyl or alkynyl, and (C₁-C₄)bridging alkyl wherein a bridge is formed between the nitrogen and acarbon atom of said alkyl or alkenyl chain containing said heteroatom toform a ring, wherein said ring is optionally fused to an Ar group; and

Z is an aromatic or tertiary alkyl amine oxidized to a correspondingN-oxide, wherein the aromatic amine is Ar oxidized to a correspondingN-oxide where Ar is a mono-, bi- or tricyclic, carbo- or heterocyclicring, wherein the ring is either unsubstituted or substituted in one tothree position(s) with halo, hydroxyl, nitro, trifluoromethyl, C₁-C₆straight or branched chain alkyl or alkenyl, C₁-C₄ alkoxy, C₁-C₄alkenyloxy, phenoxy, benzyloxy, amino, or a combination thereof; whereinthe individual ring sizes are 5-6 members; wherein the heterocyclic ringcontains 1-6 heteroatom(s) selected from the group consisting of O, N,S, and a combination thereof wherein at least one of the heteroatoms isN, and wherein the alkyl amine is oxidized to a corresponding N-oxidewhere alkyl is a C₁-C₆ straight or branched chain alkyl or alkenyl whichis optionally substituted in one or more positions with C₁-C₆ straightor branched chain alkyl or alkenyl, or C₃-C₈ cycloalkyl, or C₅-C₇cycloalkenyl, or hydroxyl, or carbonyl oxygen, or with Ar, where saidalkyl, alkenyl, cycloalkyl, cycloalkenyl, or Ar group is optionallysubstituted with C₁-C₄ alkyl, C₁-C₄ alkenyl, or hydroxy, or carbonyloxygen, or wherein any of the carbon atoms of said alkyl, alkenyl,cycloalkyl, cycloalkenyl, or Ar group is optionally replaced with C, NH,NR₁, S, SO, or SO₂; and,

R₁ is hydrogen, (C₁-C₄) -straight or branched chain alkyl, (C₃-C₄)-straight or branched chain alkenyl or alkynyl, or R₁ is Y-Z, as definedabove.

A further particularly preferred embodiment of this invention is acompound of formula IV:

or a pharmaceutically acceptable salt thereof, wherein:

n is , 1, 2 or 3 forming a 5-7 member heterocyclic ring;

W is O, S, CH₂, or H₂;

R is a C₁-C₆ straight or branched chain alkyl or alkenyl groupoptionally substituted with C₃-C₈ cycloalkyl, C₃ or C₅ cycloalkyl, C₅-C₇cycloalkenyl, or Ar₁, where said alkyl, alkenyl, cycloalkyl, orcycloalkenyl groups may be optionally substituted with C₁-C₄ alkyl,C₁-C₄ alkenyl, or hydroxy, and where Ar₁ is selected from the groupconsisting of 1-napthyl, 2-napthyl, 1-indolyl, 2-indolyl, 2-furyl,3-furyl, 2-thienyl, 3-thienyl, 2-pyridyl, 3-pyridyl, 4-pyridyl, orphenyl, having one to three substituents which are independentlyselected from the group consisting of hyrogen, halo, hydroxyl, nitro,trifluoromethyl, C₁-C₆ straight or branched alkyl or alkenyl, C₁-C₄alkenyloxy, phenoxy, benzyloxy, and amino;

X is O, NH, NR₁, S, CH, CR₁, or C(R₁)₂;

Y is a direct bond, or a C₁-C₆ straight or branched chain alkyl oralkenyl which is optionally substituted in one or more positions withC₁-C₆ straight or branched chain alkyl or alkenyl, or C₃-C₈ cycloalkyl,or C₅-C₇ cycloalkenyl, or hydroxyl, or carbonyl oxygen, or with Ar,where said alkyl, alkenyl, cycloalkyl, cycloalkenyl, or Ar group isoptionally substituted with C₁-C₄ alkyl, C₁-C₄ alkenyl, or hydroxy, orcarbonyl oxygen, or wherein any of the carbon atoms of said alkyl,alkenyl, cycloalkyl, cycloalkenyl, or Ar group is optionally replacedwith O, NH, NR₂, S, SO, or SO₂, where R₂ is selected from the groupconsisting of hydrogen, (C₁-C₄)-straight or branched chain alkyl,(C₃-C₄)-straight or branched chain alkenyl or alkynyl, and (C₁-C₄)bridging alkyl wherein a bridge is formed between the nitrogen and acarbon atom of said alkyl or alkenyl chain containing said heteroatom toform a ring, wherein said ring is optionally fused to an Ar group; and

Z is an aromatic or tertiary alkyl amine oxidized to a correspondingN-oxide, wherein the aromatic amine is Ar oxidized to a correspondingN-oxide where Ar is a mono-, bi- or tricyclic, carbo- or heterocyclicring, wherein the ring is either unsubstituted or substituted in none tothree position(s) with halo, hydroxyl, nitro, trifluoromethyl, C₁C₆straight or branched chain alkyl or alkenyl, C₁-C₄ alkoxy, C₁-C₄alkenyloxy, phenoxy, benzyloxy, amino, or a combination thereof; whereinthe individual ring sizes are 5-6 members; wherein the heterocyclic ringcontains 1-6 heteroatom(s) selected from the group consisting of O, N,S, and a combination thereof wherein at least one of the heteroatoms isN, and wherein the alkyl amine is oxidized to a corresponding N-oxidewhere alkyl is a C₁-C₆ straight or branched chain alkyl or alkenyl whichis optionally substituted in one or more positions with C₁-C₆ straightor branched chain alkyl or alkenyl, or C₁-C₉ cycloalkyl, or C₅-C₇cycloalkenyl, or hydroxyl, or carbonyl oxygen, or with Ar, where saidalkyl, alkenyl, cycloalkyl, cycloalkyl, or Ar group is optionallysubstituted with C₁-C₄ alkyl, C₁-C₄ alkenyl, or hydroxy, or carbonyloxygen, or wherein any of the carbon atoms of said alkyl, alkenyl,cycloalkyl, cycloalkenyl, or Ar group is optionally replaced with O, NH,NR₁, S, SO, or SO₂; and,

R₁ is hydrogen, (C₁-C₄)-straight or branched chain alkyl,(C₃-C₄)-straight or branched chain alkenyl or alkynyl, or R₁ is Y-Z, asdefined above.

In preferred embodiments, Ar is selected from the group consisting ofpyrrolidinyl, pyridyl, pyrimidyl, pyrazyl, pyridazyl, quinolinyl, andisoquinolinyl.

Particularly preferred compounds of the present invention include:

3-(2-3Pyridyl)-1-propyl(2S)-1-(3,3-Dimethyl-1,2-dioxo-pentyl)-2-pyrrolidinecarboxylate,N-oxide;

3-(3-Pyridyl)-1-propyl(2S)-1-(3,3-Dimethyl-1,2-dioxo-pentyl)-2-pyrrolidinecarboxylate,N-oxide;

3-(4-Pyridyl)-1-propyl(2S)-1-(3,3-Dimethyl-1,2-dioxo-pentyl)-2-pyrrolidinecarboxylate,N-oxide;

3-(2-Quinolyl)-1-propyl(2S)-1-(3,3-Dimethyl-1,2-dioxo-pentyl)-2-pyrrolidinecarboxylate,N-Oxide;

3-(3-Quinolyl)-1-propyl(2S)-1-(3,3-Dimethyl-1,2-dioxo-pentyl)-2-pyrrolidinecarboxylate,N-oxide; and

3-(4-Quinolyl)-1-propyl(2S)-1-(3,3-Dimethyl-1,2-dioxo-pentyl)-2-pyrrolidinecarboxylate,N-oxide.

The present invention also relates to a pharmaceutical compositioncomprising a neurotrophically effective amount of the compound offormula I, II, III, or IV, and a pharmaceutically acceptable carrier.

The present invention further includes methods of using the compounds ofthe present invention. One preferred embodiment includes a method ofstimulating damaged neurons in an animal, comprising:

administering to the animal neurotrophically effective amount of acompound of the present invention.

Another preferred embodiment of the present invention includes a methodof promoting neuronal regeneration in an animal, comprising:

administering to the animal a neurotrophically effective amount of acompound of the present invention.

Yet another embodiment of the present invention includes a method ofpreventing neurodegeneration in an animal, comprising:

administering to the animal a neurotrophically effective amount or acompound of the present invention.

Another embodiment includes a method of treating neurological disordersin an animal, comprising:

administering to the animal a neurotrophically effective amount of acompound of the present invention.

The neurological disorders for which the compounds of the presentinvention are particularly useful are selected from the group consistingof: peripheral neuropathy caused by physical injury or disease state,physical damage to the brain, physical damage to the spinal cord, strokeassociated with brain damage, and neurological disorder relating toneurodegeneration. Examples of neurological disorders relating toneurodegeneration are Alzheimer's Disease, Parkinson's Disease, andamyotrophic lateral sclerosis.

BRIEF DESCRIPTION OF THE INVENTION

FIG. 1 is a bar graph showing Protection of Striatal TH InnervationDensity from MPTP-toxicity by Concurrent Drug Dosing. FIG. 1 shows thatat administration of 4 mg/kg of the compounds of the present inventionthere is a remarkable projection or striatal nerves from MPTP-toxicity.

DETAILED DESCRIPTION OF THE INVENTION DEFINITIONS

“Alkyl” means a branched or unbranched saturated hydrocarbon chaincontaining 1 to 6 carbon atoms such as methyl, ethyl, propyl,iso-propyl, butyl, iso-butyl, tert-butyl, n-pentyl, n-hexyl, and thelike, unless otherwise indicated.

“Alkoxy” means the group -OR wherein R is alkyl as herein defined.Preferably, R is a branched or unbranched saturated hydrocarbon chaincontaining 1 to 3 carbon atoms.

“Halo” means fluoro, chloro, bromo, or iodo, unless otherwise indicated.

“Phenyl” includes all possible isomeric phenyl radicals, optionallymonosubstituted or multi-substituted with substituents selected from thegroup consisting of alkyl, alkoxy, hydroxy, halo, and haloalkyl.

The term “C₁-C₅” and similar terminology found in standard chemicalnomenclature, when used for alkyl and alkenyl chains, is known in theart to include subchains such as C₁-C₃, C₁-C₄, C₁-C₅, C₁-C₆, C₂-C₄,C₂-C₅, C₂-C₅, C₃-C₅, C₃-C₅, C₄-C₅, and the variants thereof.

The term “pharmaceutically acceptable salt” refers to sales of thesubject compounds which posses the desired pharmacological activity andwhich are neither biologically nor otherwise undesirable. The salts canbe formed with inorganic acids such as acetate, adipate, alginate,aspartate, benzoate, benzenesulfonate, bisulfate butyrate, citrate,camphorate, camphorsulfonate, cyclopentanepropionate, digluconate,dodecylsulfate, ethanesulfonate, fumarate, glucoheptanoate,glycerophosphate, hemisulfate, heptanoate, hexanoate, hydrochloridehydrobromide, hydroiodide, 2-hydroxyethanesulfonate, lactate, maleate,methanesulfonate, 2-naphthalenesulfonate, nicotinate, oxalate,thiocyanate, tosylate and undecanoate. Base salts include ammoniumsalts, alkali metal salts such as sodium and potassium salts, alkalineearth metal salts such as calcium and magnesium salts, salt with organicbases such as dicyclohexylamine salts, N-methyl-D-glucamine, and saltswith amino acids such as arginine, lysine, and so forth. Also, the basicnitrogen-containing groups can be quarternized with such agents as loweralkyl halides, such as methyl ethyl, propyl, and butyl chloride,bromides and iodides; dialkyl sulfates like dimethyl, diethyl, dibutyland diamyl sulfates, long chain halides such as decyl, lauryl, myristyland stearyl chlorides, bromides and iodides, aralkyl halides like benzyland phenethyl bromides and others. Water or oil-soluble or dispersibleproducts are thereby obtained.

The compounds of this invention possess at least one asymmetric centerand thus can be produced as mixtures of stereoisomers or as individualenantiomers or diastereomers. The individual stereoisomers may beobtained by using an optically active starting material, by resolving aracemic or non-racemic mixture or an intermediate at some appropriatestage of the synthesis, or by resolution of the compound of formula (I).It is understood that the individual stereoisomers as well as mixtures(racemic and non-racemic) of stereoisomers are encompassed by the scopeof the present invention. The S-stereoisomer at atom 1 of formula I ismost preferred due to its greater activity

“Isomers” are different compounds that have the same molecular formula.

“Stereoisomers” are isomers that differ only in the way the atoms arearranged in space.

“Enantiomers” are a pair of stereoisomers that are non-superimposablemirror images or each other.

“Dieastereoisomers” are stereoisomers which are not mirror images ofeach other.

“Racemic mixture” means a mixture containing equal parts or individualenantiomers. “Non-racemic mixture” is a mixture containing unequal partsso individual enantiomers or stereoisomers.

The term “treatment” as used herein covers any treatment or a diseaseand/or condition in an animal, particularly a human, and includes:

(i) preventing a disease and/or condition from occurring in a subjectwhich may be predisposed to the disease and/or condition but has not yetbeen diagnosed as having it;

(ii) inhibiting the disease and/or condition, i.e., arresting itsdevelopment; or

(iii) relieving the disease and/or condition, i.e., causing regressionof the disease and/or condition.

The term “effecting” as directed to “effecting neuronal activity”activity relates to producing or bringing about a desired effect orresult and includes without limitation stimulating neurons, promotingregeneration preventing degeneration, protecting from degeneration andtreating disorders.

The system used in naming the compounds of the present invention isshown below, using a compound of formula IV as an example.

A compound of the present invention, especially Formula IV, wherein n is1, R is 1,1-dimethylpropyl, X is O, Y is (CH₂)₃, and Z is3-pyridyl-N-oxide, is named 3-(3-Pyridyl)-1-propyl(2S)-1-(3,3-Dimethyl-1,2-dioxopentyl)-2-pyrrolidinecarboxylate, N-oxide.

COMPOUNDS OF THE INVENTION

The neurotrophic low molecular weight, small molecule FKBP inhibitorcompounds of this invention have an affinity for FKBP-typeimmunophilins, such as FKBP12. When the neurotrophic compounds of thisinvention are bound to an FKBP-type immunophilin, they have been foundto inhibit the prolyl-peptidyl cis-trans isomerase activity, orrotamase, activity of the binding protein and unexpectedly stimulateneurite growth.

Specific exemplifications of these embodiments are presented in TABLE I.

TABLE I

No. n X Y Z R 1 1 O (CH₂)₃ 3-Pyridyl N-oxide 1,1-dimethylpentyl 2 1 O(CH₂)₃ 2-Pyridyl N-oxide 1,1-dimethylpentyl 3 1 O (CH₂)₃ 4-PyridylN-oxide 1,1-dimethylpentyl 4 1 O (CH₂)₃ 2-Quinolyl N-oxide1,1-dimethylpentyl 5 1 O (CH₂)₃ 3-Quinolyl N-oxide 1,1-dimethylpentyl 61 O (CH₂)₃ 4-Quinolyl N-oxide 1,1-dimethylpentyl

The most preferred compounds of formula IV are:

3-(2-Pyridyl)-1-propyl(2S)-1-(3,3-Dimethyl-1,2-dioxo-pentyl)-2-pyrrolidinecarboxylate,N-oxide;

3-(3-Pyridyl)-1-propyl(2S)-1-(3,3-Dimethyl-1,2-dioxo-pentyl)-2-pyrrolidinecarboxylate,N-oxide;

3- (4-Pyridyl)-1propyl(2S)-3-(3,3-Dimethyl-1,2-dioxo-pentyl)-2-pyrrolidinecarboxylate,N-oxide;

3-(2-Quinolyl)-1-propyl(2S)-1-Dimethyl-1,2-dioxo-pentyl)-2-pyrrolidinecarboxylate, N-oxide;

3-(3-Quinolyl)-1-propyl(2S)-1-(1,1-Dimethyl-1,2-dioxo-pentyl)-2-pyrrolidinecarboxylate,N-oxide; and

3-(4-Quinolyl)-1-propyl(2S)-1-(1,1-Dimethyl-1,2-dioxo-pentyl)-2-pyrrolidinecarboxylate,N-oxide.

The compounds of the present invention exist as stereoisomeric forms,either enantiomers or diastereoisomers. Included within the scope of theinvention are the enantiomers, the racemic form, and diastereoisomericmixtures. Enantiomers and diastereoisomers can be separated by methodsknown to those skilled in the art.

Methods of Using the Compounds of the Invention

The compounds of the present invention have an affinity for the FK506binding protein, particularly FKBP12 which is present in the neuronaltissue. When the inventive compounds bind To FKBP in neuronal tissue,they exhibit excellent neurotrophic activity This activity is useful inthe stimulation or damaged neurons, the promotion of neuronalregeneration, the prevention of neurodegeneration, the protection ofnerves from neurodegeneration, and the treatment of several neurologicaldisorders known to be associated with neuronal degeneration andperipheral neuropathies.

For the foregoing reasons, the present invention further relates to amethod of effecting a neuronal activity in an animal, comprising:

administering to the animal a neurotrophically effective amount of acompound of formula I, II, III in a preferred embodiment, the neuronalactivity or IV.

In a preferred embodiment, the neuronal activity is selected from thegroup consisting of stimulation of damaged neurons, promotion ofneuronal regeneration, prevention of neurodegeneration, protection ofneurodegeneration, and treatment of neurological disorder.

The neurological disorders that may be treated include but are notlimited to: trigeminal neuralgia; glossopharyngeal neuralgia; Bell'sPalsy; myasthenia gravis; muscular dystrophy; amyotrophic lateralsclerosis; progressive muscular atrophy; progressive bulbar inheritedmuscular atrophy; herniated; ruptured or prolapsed invertebrate disksyndromes; cervical spondylosis; plexus disorders; thoracic outletdestruction syndromes; peripheral neuropathic such as those caused bylead, dapsone, ticks, porphyria, or Guillain-Barré syndrome; Alzheimer'sdisease; and Parkinson's disease.

The compounds of the present invention are particularly useful fortreating a neurological disorder selected from the group consisting of:peripheral neuropathy caused by physical injury or disease state,physical damage to the brain, physical damage to the spinal cord, strokeassociated with brain damage, and neurological disorder relating toneurodegeneration. Examples of neurological disorders relating toneurodegeneration are Alzheimer's Disease, Parkinson's Disease, andamyotrophic lateral sclerosis.

Pharmaceutical Compositions and Formulations

For these purposes the compounds of the present invention may beadministered orally, parenterally, by inhalation spray, topically,rectally, nasally, buccally, vaginally or via an implanted reservoir indosage formulations containing conventional non-toxicpharmaceutically-acceptable carriers, adjuvants and vehicles. The termparenteral as used herein includes subcutaneous, intravenous,intramuscular, intraperitoneally, intrathecally, intraventricularly,intrasternal and intracranial injection or infusion techniques.

To be effective therapeutically as central nervous system targets, thecompounds of the present invention should readily penetrate theblood-brain barrier when peripherally administered. Compounds whichcannot penetrate the blood-brain barrier can be effectively administeredby an intraventricular route or other appropriate delivery systemsuitable for administration to the brain.

The compounds of the present invention may be administered in the formof sterile injectable preparations, for example, as sterile injectableaqueous or oleaginous suspensions. These suspensions may be formulatedaccording to techniques known in the art using suitable dispersing orwetting agents and suspending agents. The sterile injectablepreparations may also be sterile injectable solutions or suspensions Innon-toxic parenterally-acceptable diluents or solvents, for example, assolutions in 1,3-butanediol. Among the acceptable vehicles and solventsthat may be employed are water, Ringer's solution and isotonic sodiumchloride solution. In addition, sterile, fixed oils are conventionallyemployed as solvents or suspending mediums. For this purpose, any blandfixed oil may be employed including synthetic mono- or di-glycerides.Fatty acids such as oleic acid and its glyceride derivatives, includingolive oil and castor oil, especially in their polyoxyethylated versions,are useful in the preparation of injectables. These oil solutions orsuspensions may also contain long-chain alcohol diluents or dispersants.

The compounds may be administered orally in the form of capsules,tablets, aqueous suspensions or solutions. Tablets may contain carrierssuch as lactose and corn starch, and/or lubricating agents such asmagnesium stearate. Capsules may contain diluents including lactose anddried corn starch. Aqueous suspensions may contain emulsifying andsuspending agents combined with the active ingredient. The oral dosageforms may further contain sweetening and/or flavoring and/or coloringagents.

The compounds of this invention may also be administered rectally in theform of suppositories. These compositions can be prepared by mixing thedrug with a suitable non-irritating excipient which is solid at roomtemperature, but liquid at rectal temperature and, therefore, will meltin the rectum to release the drug. Such materials include cocoa butter,beeswax and polyethylene glycols.

The compounds of this invention may also be administered topically,especially when the conditions addressed for treatment involve areas ororgans readily accessible by topical application, including neurologicaldisorders of the eye, the skin, or the lower intestinal tract. Suitabletopical formulations are readily prepared for each of these areas.

For topical application to the eye, or ophthalmic use, the compounds canbe formulated as micronized suspensions in isotonic, Ph adjusted sterilesaline, or, preferably, as solutions in isotonic, Ph adjusted sterilesaline, either with or without a preservative such as benzylalkoniumchloride. Alternatively for the ophthalmic uses the compounds may beformulated in an ointment such as petrolatum.

For topical application to the skin, the compounds can be formulated ina suitable ointment containing the compound suspended or dissolved in,for example, a mixture with one or more of the following: mineral oil,liquid petrolatum, white petrolatum, propylene glycol, polyoxyethylenepolyoxypropylene compound, emulsifying wax and water. Alternatively, thecompounds can be formulated in a suitable lotion or cream containing theactive compound suspended or dissolved in, for example, a mixture of oneor more of the following: mineral oil, sorbitan monostearate,polysorbate 60, cetyl esters wax, cetearyl alcohol, 2-octyldodecanol,benzyl alcohol and water.

Topical application for the lower intestinal tract an be effected in arectal suppository formulation (see above) or in a suitable enemaformulation.

Dosage levels on the order of about 0.1 mg to about 10,000 mg of theactive ingredient compound are useful in the treatment of the aboveconditions, with preferred levels of about 0.1 mg to about 1,000 mg. Theamount of active ingredient that may be combined with the carriermaterials to produce a single dosage form will vary depending upon thehost treated and the particular mode of administration.

It is understood, however, that a specific dose level for any particularpatient will depend upon a variety of factors including the activity ofthe specific compound employed, the age, body weight, general health,sex, diet, time of administration, rate of excretion, drug combination,and the severity of the particular disease being treated and form ofadministration.

The compounds can be administered with other neurotrophic agents such asneurotrophic growth factor (NGF) glial derived growth factor, brainderived growth factor, ciliary neurotrophic factor, and neurotropin-3.The dosage level of other neurotrophic drugs will depend upon thefactors previously stated and the neurotrophic effectiveness of the drugcombination.

As discussed above, the compounds of the present invention have anaffinity for the FK506 binding protein, particularly FKBP12. Theinhibition of the prolyl peptidyl cis-trans isomerase activity of FKBPmay be measured as an indicator of this affinity.

Ki Test Procedure

Inhibition of the peptidyl-prolyl isomerase (rotamase) activity of theinventive compounds can be evaluated by known methods described in theliterature (Harding, et al., Nature, 1989, 341 :758-760; Holt et al. J.Am. Chem. Soc., 115:9923-91938). These values are obtained as apparentKi's and are presented in Table II. The cis-trans isomerization of analanine-proline bond in a model substrate,N-succinyl-Ala-Ala-Pro-Phe-p-nitroanilide, is monitoredspectrophotometrically in a chymotrypsin-coupled assay, which releasespara-nitroanilide from the trans form of the substrate. The inhibitionof this reaction caused by the addition of different concentrations ofinhibitor is determined, and the data is analyzed as a change infirst-order rate constant as a function of inhibitor concentration toyield the apparent Ki values.

In a plastic cuvette are added 950 ml of ice cold assay buffer (25 mMHEPES, pH 7.8, 100 mM NaCl), 10 mL of FKBP (2.5 mM dithiothreitol) 25 mLof chymotrypsin (50 mg/ml in 1 mM HCL) and 10 mL of test compound atvarious concentrations in dimethyl sulfoxide. The reaction is initiatedby the addition of 5 mL of substrate(succinyl-Ala-Phe-Pro-Phe-para-nitroanilide, 5 mg/mL in 2.35 mM LiCl intrifluoroethanol).

The absorbance at 390 nm versus time is monitored for 90 seconds using aspectrophotometer and the rate constants are determined from theabsorbance versus time data files.

The data for these experiments for representative compounds arepresented in Table II under the column “Ki”.

The neurotrophic effects of the compounds of the present invention canbe demonstrated in cellular biological experiments in vitro, asdescribed below.

Chick Dorsal Root Ganglion Cultures and Neurite Growth

Dorsal root ganglia were dissected from chick embryos of ten daygestation. Whole ganglion explants were cultured on thin layerMatrigel-coated 12 well plates with Liebovitz L15 plus high glucosemedia supplemented with 2 mM glutamine and 10% fetal calf serum, andalso containing 10 μM cytosine β-D arabinofuranoside (Ara C) at 37° C.in an environment containing 5% CO₂. Twenty-four hours later, the DRGsForty-eight hours after drug treatment, the ganglia were visualizedunder phase contrast or Hoffman Modulation contrast with a ZeissAxiovert inverted microscope. Photomicrographs of the explants weremade, and neurite outgrowth was quantified. Neurites longer than the DRGdiameter were counted as positive, with total number of neuritesquantitated per each experimental condition. Three to four DRGs arecultured per well, and each treatment was performed in duplicate.

The unexpectedly greater metabolic stability of the N-oxides of thepresent invention may be demonstrated in vitro assays. In studies todirectly asses the rate of metabolism of N-oxides, a mouse livermicrosomal assay was used as described below to model first passmetabolism. Data is presented comparing the N-oxide of Example 1 withits parent (unoxidized) compound, showing the N-oxide has asignificantly longer half-life than the parent compound. Additionally,studies using purified esterification enzyme (described in detail below)demonstrated that Example 1 undergoes limited de-esterification in vitroduring the course of the study whereas the precursor compound(unoxidized parent compound) undergoes significant degradation under thesame reaction conditions.

Microsomal Assay

Liver microsomes from various species were purchased from a commercialsupplier. The microsomes are characterized prior to shipment. Thereaction mixture contained microsomes, 5 μM MgCl₂, 1 mM NADP, 4 mMglucose-6-phosphate (G-6-P), and 1 unit/4 mL glucose-6-phosphatedehydrogenase (G-6-P DH). The final microsomal protein concentration forall studies was 0.2 mg/mL. Incubations were carried out for 1 hour in ashaking water bath (37° C.). The reaction was terminated by removing analiquot from the reaction mixture and placing it in a tube with an equalvolume of acetonitrile and the bioanalytical internal standard. Theresults of these experiments are presented as compound half-lives(t_(1/2)) in Table II.

Esterase Activity

Purified rabbit liver esterase was purchased from Sigma. Five (5) unitsof enzyme were placed in 2 mL of 0.05 M Tris buffer (pH 7.5).Incubations were performed for 2 hours. The reaction was terminated byremoving an aliquot from the reaction mixture and placing it in a tubewith an equal volume of acetonitrile and the bioanalytical internalstandard. The results of these experiments are presented in Table II asrates of enzymatic degradation of the compounds.

The results of these in vitro experiments for 3-(3-Pyridyl)-1-propyl(2S)-1-(3,3-Dimethyl-1,2-dioxopentyl)-2-pyrrolidinecarboxylate(“Parent”) are tabulated in Table II.

TABLE II esterase degradation K_(i) ED₅₀ t_(1/2) (pmol/min/mg Compound(nM) (nM) (min) protein) Parent 7.5 0.05 8.1 7521 Example 1 225 2.2 42.8 367

MPTP Model of Parkinson's Disease

The remarkable neurotrophic and neuroregenerative effects of the presentinventive compounds can be further demonstrated in an animal model ofneurodegenerative disease. MPTP lesioning of dopaminergic neurons inmice is used as an animal model of Parkinson's Disease. Four week oldmale CD1 white mice are dosed i.p. with 30 mg/kg of MPTP for 5 days.Test compounds (4 mg/kg), or vehicle, are administered s.c. along withthe MPTP for 5 days, as well as for an additional five days followingcessation of MPTP treatment. At 18 days following MPTP treatment, theanimals are sacrificed and the striata dissected and perfusion-fixed.Immunostaining is performed on sagittal and coronal brain sections usinganti-tyrosine hydroxylase 1 g to quantitative survival and recovery ofdopaminergic neurons. In animals treated MPTP and vehicle, a substantialloss of functional dopaminergic terminals is observed as compared tonon-lesioned animals. Lesioned animals receiving test compounds show asignificant recovery of TH-stained dopaminergic neurons. This modelpresents quantitation for the recovery of TH-positive dopaminergicneurons in the striatum of animals receiving of animals receiving thecompounds of the present invention. Data for representative control andlesioned animals not receiving the test drugs is also presented againstthe data from the animals receiving the compounds of the presentinvention.

Data for the representative control and lesioned animals not receivingtest drugs is presented against the Parent compound and Example 1 of thepresent invention in FIG. 1. It is clear that, although Example 1 isless potent in vitro, it is more potent in this in vivo model ofneurodegeneration, due to its unexpectedly better bioavailability andpharmacokinetics.

EXAMPLES

The following examples are illustrative of the present invention and arenot intended to be limitations thereon.

Example 1

Synthesis of 3-(3-Pyridyl)-1-propyl(2S)-1-(3,3-Dimethyl-1,2-dioxopentyl) -2-pyrrolidinecarboxylate,N-oxide. (1)

Methyl (2S) -1- (1,2-dioxo-2-methoxyethyl) -2-pyrrolidinecarboxylate. Asolution of L-proline methyl ester hydrochloride (3.08 g; 18.60 mmol) indry methyl chloride was cooled to 0° C. and treated with triethylamineamine (3.92 g; 38.74 mmol; 2.1 eq). After stirring the formed slurryunder a nitrogen atmosphere for 15 min, a solution of methyl oxalylchloride (3.20 g; 26.12 mmol) in methylene chloride (45 mL) was addeddropwise. The resulting mixture was stirred at 0° C. for 1.5 hr. Afterfiltering to remove solids, the organic phase was washed with water,dried over MgSO₄ and concentrated. The crude residue was purified on asilica gel column, eluting with 50% ethyl acetate in hexane, to obtain3.52 g (88%) of the product as a reddish oil. Mixture of cis-trans amiderotamers; data for trans rotamer given. ¹H NMR (CDCl₃): 67 1.93 (dm,2H); 2.17 (m, 2H); 3.62 (m, 2H): 3.71 (s, 3H); 3.79, 3.84 (s, 3H total);4.86 (dd, 1H, J=8.4, 3.3).

Methyl (2S)-1-(1,2-dioxo-3,3-dimethylpentyl) -2-pyrrolidinecarboxylate.A solution of methyl(2S)-1-(1,2-dioxo-2-methoxyethyl)-2-pyrrolidinecarboxylate (2.35 g;10.90 mmol) in 30 mL of tetrahydrofuran (THF) was cooled to −78° C. andtreated with 14.2 mL of a 1.0 M solution of 1,1-dimethylpropylmagnesiumchloride in THF. After stirring the resulting homogeneous mixture at−78° C. for three hours, the mixture was poured into saturated ammoniumchloride (100 mL) and extracted into ethyl acetate. The organic phasewas washed with water, dried, and concentrated, and the crude materialobtained upon removal of the solvent was purified on a silica gelcolumn, eluting with 25% ethyl acetate in hexane, to obtain 2.10 g (75%)of the oxamate as a colorless oil. ¹H NMR (CDCl₃): δ 0.88 (t,3H); 1.22,1.26 (s,3H each); 1.75 (dm, 2H); 1.87-2.10 (m,3H) 2.23 (m, 1H); 3.54 (m,2H); 3.76 (s, 3H) 4.52(dm, 1H, J=8.4, 3.4).

(2s)-1-(1, 2-dioxo-3,3-dimethylpentyl)-2-pyrrolidinecarboxylic acid. Amixture of methyl (2S)-1-(1,2-dioxo-3,3-dimethylpentyl-2-pyrrolidinecarboxylate (2.10 g; 8.23 mmol), 1N LiOH (15 mL), and methanol (50 mL) was stirred at 0° C. for 30 min andat room temperature overnight. The mixture was acidified to pH 1 with 1N HCl, diluted with water, and extracted into 100 mL of methylenechloride. The organic extract was washed with brine and concentrated todeliver 1.73 g (87%) of snow-white solid which did not require furtherpurification. ¹H NMR (CDCl₃):d 0.87 (t,3H); 1.22, 1.25 (s,3H each); 1.77(dm,2H); 2.02 (m,2H); 2.17 (m, 1H); 2.25 (m,1H); 3.53 (dd, 2H, J=10.4,7.3); 4.55 (dd, 1H, J=8.6, 4.1).

3-(3-Pyridyl)-1-propyl(2S)-1-(3,3-dimethyl-1,2-dioxopentyl)-2-pyrrolidinecarboxylate. Amixture of 2S)-1-(1,2-dioxo-3,3-dimethylpentyl)-2-pyrrolidinecarboxylicacid (4.5 g; 19 mmol), 3-pyridinepropanol (3.91 g; 28.5 mmol),dicyclohexylcarbodiimide (6.27 g; 30.4 mmol), camphorsulphonic acid(1.47 g; 6.33 mmol) and 4-dimethyl aminopyridine (773 mg; 6.33 mmol) inmethylene chloride (100 mL) was stirred overnight under a nitrogeneatmosphere. The reaction mixture was filtered through Celite to removesolids and concentrate in vacuo. The crude material was triturated withseveral portions of ether, and the ether portions were filtered throughCelite to remove solids and concentrated in vacuo. The concentratedfiltrate was purified on a flash column (gradient elution, 25%ethylacetate in hexane to pure ethyl acetate) to obtain 5.47 g (80%) of GPI1046 as a colorless oil (partial hydrate). ¹H NMR (CDCl₃, 300 MHz): δ0.85 (t, 3H); 1.23, 1.26 (s,3H each); 1.63-1.89 (m, 2H); 1.90-2.30 (m,4H; 2.30-2.50 (m,1H); 2.72(t, 2H,) 3.53 (m, 2H); 4.19 (m, 2H); 4.53(m,1H); 7.22 (m, 1H) 7.53 (dd, 1H); 8.45. Anal. Calcd. for C₂₀H₂₈No₄ -0.25H₂O:C, 65.82; H, 7.87; N, 7.58. Found: C, 66.01; H, 7.85; N, 7.64.

3-(3-Pyridyl)-1-propyl(2S)-1-(3.3-dimethyl-1,2-dioxopentyl)-2-pyrrolidinecarboxylate, N-oxide.A solution of 3-(3-pyridyl)-1-propyl(2S)-1-(3,3-dimethyl-1,2-dioxopentyl)-2-pyrrolidinecarboxylate (190 mg;0.52 mmol) and m-chloroperbenzoic acid (160 mg of 57%-88% material, 0.53mmol) was stirred in methylene chloride (20mL) at room temperature for 3hrs. The reaction-mixture was diluted with methylene chloride and washedtwice with IN NaOH. The organic extract was dried and concentrated andthe crude material was chromatographed, eluting with 10% methanol inethyl acetate, to obtain 130 mg of the compound of Example 1, ¹H NMR(CDCl³, 300 MHz): δ0.83 (t,3H); 1.21 (s,3H); 1.25 (s,3H); 1.75-2.23 (m,8H); 2.69 (t,f2H, J=7.5); 3.52 (t,2H, J-6.3); 4. 17 (dd, 2H, J=6.3);4.51 (m, 1H); 7.16-7.22 (m,2H); 8.06-8.1 (m, 2H). Anal. Calcd. forC₂₀H₂₈N₂O₅ -0.75 H₂O: C,61.60; H,7.63; N,7.18. Found: C,67.79; H, 7.58;N, 7.23.

What is claimed is:
 1. A low molecular weight, small molecule N-oxide ofa heterocyclic ester, amide, thioester or ketone compound.
 2. Thecompound of claim 1, wherein the compound is non-immunosuppressive. 3.The compound of claim 1, wherein the compound is neurotrophic.
 4. Apharmaceutical comosition comprising a neurotrophically effective amountof a low molecular weight, small molecule N-oxide of a heterocyclicester, amide, thioester, or ketone compound, and pharmaceuticallyacceptable carrier.
 5. A method of promoting neuronal growth andregeneration in various neuropathological situations where neuronalrepair can be facilitated in an animal, comprising: administering to theanimal a neurotrophically effective amount of a non-immunosuppressivelow molecular weight, small molecule N-oxide of a heterocyclic ester,amide, thioester, or ketone compound.
 6. The method of claim 5, whereinthe neuropathological situations are selected from the group consistingof peripheral neuropathy caused by physical injury or disease state,physical damage to the brain, physical damage to the spinal cord, strokeassociated with brain damage, and neurological disorders relating toneurodegeneration.
 7. The method of claim 6, wherein the neurologicaldisorder relating to neurodegeneration is selected from the groupconsisting of Alzheimer's Disease, Parkinson's Disease, and amyotrophiclateral sclerosis.